Getting truck to run cooler

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HawkeyeScott

HawkeyeScott

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I towed our travel trailer with our '08 5.3 Suburban over the weekend in what was still some fairly cool weather (60s and lower 70s). Despite the ambient temps, the truck's water temp got warmer than it usually does while towing the same trailer. It runs normally at 210. I was close to 235 degrees during a couple of long mountain pulls, despite only going about 35 or 40 mph. Engine wasn't revving above 2500 RPMs.

The only thing that has changed in the cooling system was a new thermostat I installed this spring, and the installation of new coolant to bring it back up to the Full mark. I did a 50-50 mix of water and DexCool.

Would increasing the mix ratio to include more coolant and less water bring help bring those temps down a bit?
 
What's the temp rating on the new thermostat?

Could there be air in the cooling system from the coolant change?

Also check that the fan is running correctly.

And is the water pump original to the car?
 
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Is that still a mechanical clutch fan? Not sure when they switched to the electric. If its a mechanical fan, it sounds like its shot.
And, more coolant will run hotter. Coolant has less thermal capacity than plain water, so you'd end up hotter.
To Saab's list, I'd add check the coolant cap. Ive had a few of those fail and not hold their rated pressure.
 
If I recall correctly, water does better at carry heat than the coolant, so you'd want to run more water and less coolant. But either way, I wouldn't mess with that. I'd check everything else first, like the radiator (maybe try straighten fins?), radiator fan, water pump, and transmission cooler if you have one (or if it runs the transmission cooler through the radiator).

Based on the changes you made, the thermostat is an obvious component to check.
 
1. Adjust coolant mixture to reflect the lowest temp your truck will see. I live in Southern Ontario, and I think I can get away with less than 50/50, I recently fixed a coolant leak after diluting heavily with distilled and I've been meaning to fine tune my mixture. I also used dex and it looks a little thick, I tried to put 75% coolant in to compensate for the dilution but I think that may have been over zealous.
2. Clean your radiator. I just cleaned my AC condenser and it was right up against the front of the rad. Cleaning the radiator from the front might be hard, but if there is room to clean it from behind that might be better, but make sure you rinse it thoroughly if you use a detergent, you can just use normal AC coil cleaner
3. How did the coolant look when you drained it? If it was gross consider flushing it, with or without a flush additive. If I had cooling problems that I thought were caused by blockages or junk in the coolant, I would probably try a citric acid flush if it was compatible with my car.

It would seem that:
1. New thermostat could be a higher temperature than the old one, this seems likely as you only noticed lack of cooling capacity when you started towing.
2. Something went wrong when you filled and bled the coolant, but you would think that would be apparent before you towed with it.
 
Thanks all. I replaced the thermostat with the same stock AC Delco. Prior to the recent trip, it's behaved exactly as the other one did before it began to fail. The thermostat change and refill/system burp happened two months ago. The coolant level in the reservoir hasn't changed during that period.

Not sure about water pump being original. It is the same one that was used last summer, though. Fans seem to be working the way they normally do.

The trailer, loaded, is about 60 percent of the truck's towing capacity. I traveled the same roads with the same truck and trailer last year and never quite got the truck this warm.

Lowest temps we get here are around -10. 50-50 mix has me well below that. I could cut the coolant and still be okay. Which I might try if spraying the radiator out doesn't do the trick.

Thanks again, everyone. I appreciate you taking a minute to weigh in.
 
Clean the rad. Any time I drop coolant in a vehicle I remove the rad and give it a LIGHT power washing....always amazed at the amount of gunk that comes out of the fins.
 
Drive it around then let it sit and idle to make sure the fans come on. Then I would clean the outside of the ac condenser and radiator gently with a brush to get the bugs then with some simple green or whatever and the hose. Back to front also if possible. Then I would probably replace the coolant cap.
 
Originally Posted By: HawkeyeScott
I replaced the thermostat with the same stock AC Delco. Prior to the recent trip, it's behaved exactly as the other one did before it began to fail.


Either the thermostat is bad, or something else is wrong with your cooling system. Are you sure the old thermostat was bad?

If it is having trouble cooling under load, you might want to take a look at your water pump, especially if your only towing a moderate load. I had a bad thermostat that failed open and I could watch coolant temps with my scangauge. It would get to about 160 F and stay there unless it was really hot. I also had a bad cooling fan which I found after I changed the thermostat.
 
Agree with most of the above, wouldn't be the first time a new thermostat was bad.

Radiators do get coated with scale on the inside over time.
 
Originally Posted By: PiperOne
Clean the rad. Any time I drop coolant in a vehicle I remove the rad and give it a LIGHT power washing....always amazed at the amount of gunk that comes out of the fins.

A garden hose with a nozzle would be a better choice than a power washer, especially on an aluminum radiator. Many years ago I cleaned the aluminum radiator on a dirt modified racecar, and spent the rest of the week straightening like a thousand fins I had flattened out on both sides, with the pressure washer.
 
Originally Posted By: Traction
Originally Posted By: PiperOne
Clean the rad. Any time I drop coolant in a vehicle I remove the rad and give it a LIGHT power washing....always amazed at the amount of gunk that comes out of the fins.

A garden hose with a nozzle would be a better choice than a power washer, especially on an aluminum radiator. Many years ago I cleaned the aluminum radiator on a dirt modified racecar, and spent the rest of the week straightening like a thousand fins I had flattened out on both sides, with the pressure washer.

I used a garden hose using the setting you would use to water plants just to be sure of no damage, but it took forever to rinse the detergent I used completely out of the condenser + rad.

I can see where he is coming from suggesting it, it would really help blast the junk out. I'm not sure a hose even on the jet setting would really be able to penetrate between the fins. I think pressure washers drop off in pressure pretty quickly, I've blasted my leg/hand a few times accidently from like a foot away and it didn't even hurt. This was just a homeowner grade electric though.
 
yep...if the rad has been cleaned exterior-wise, make sure the fins are all straight. No air will be getting through any parts with bent fins.
 
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When I say LIGHT power wash I mean the washer is turned down to around 700 psi and I'm standing about 3 or 4 feet away using a wide fan nozzle.....not hitting the fins with 4000 psi in an attempt to clean inside the rad from the outside.
smirk.gif
 
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